Thanks I nornally only run my mathmos lamps for about 6 hours or less. I did leave one on one night when i was tired and feel asleep. Thanks bohdan for advise about the metallics i run mine now off a 30w bulb.
I wouldn't run my lamps for more than 10 hours although I have done before (falling asleep) but to no ill-effect, as long as you don't do this too regularly. I read here once that an ex-member ran a Mathmos Telstar for 3 years continuously! All the lava turned white apparently.